The present invention relates to heating circuits and, more particularly, to heating circuits in conveyor ovens.
Electric heating elements are used in infrared cooking ovens, including infrared conveyor ovens used to cook pizzas and other foods. Electric heating elements can be controlled by solid-state, zero-cross relays. In particular, the supply of electrical power to the heating elements is controlled by the relays. Electrical noise is generated when relay contacts open and close and zero-cross relays generate less noise than other types of relays. As with most components, solid-state relays are subject to failure and if a relay fails in the on position, a constant supply of power is provided to the heating element. This could lead to over-heating and other hazards. A coil-activated or triggered contactor can be used in the circuit prior to (or in series with) the solid-state relays to provide a safety (or circuit break) in case a solid-state relay fails in the on position. A high-temperature-limit-control switch operates the contactor coil and, if the high limit is tripped, the coil to the contactor is de-energized and the contactor opens. When the contactor opens, the supply of power to the heating element is interrupted.